Two former prime ministers went head-to-head on Sunday in a runoff vote for France's center-right presidential nomination, with the victor expected to face a showdown against a resurgent far-right in May.
The winner, either Francois Fillon or Alain Juppe, will most likely represent the entire French political mainstream against the National Front's Marine Le Pen, in another test of the anti-establishment anger in Western countries that saw Britain vote to leave the EU and Americans elect Donald Trump as president.
Opinion polls show Fillon, a social conservative with a deep attachment to France's Catholic roots, as the clear favorite after stunning his more centrist challenger with a surge in support just before the Nov. 20 party nomination first round.
Voting opened at more than 10,000 polling stations across France at 8 a.m. (0700 GMT) and was set to close at 7 p.m., with the first results likely up to an hour and a half later.
Organizers from the center-right party, which took the name Les Republicains last year, said that by midday the participation rate was 10 to 15 percent higher than in last week's first round.
A 62-year-old racing car enthusiast who lives in a Loire valley chateau, Fillon promises radical reforms to France's regulation-encumbered economy, vowing to roll back the state and slash government's bloated costs.
Scrambling to regain momentum, Juppe, 71, a soft-mannered moderate who is now mayor of Bordeaux, has attacked the "brutality" of his rival's reform program and says the Paris lawmaker lacks credibility.
But in a blow to Juppe, television viewers found the harder-line Fillon more convincing in a head-to-head debate on Thursday.
"He's not ashamed of being on the right, and even less of being Catholic," Fillon backer Valerie Sonnard, a childminder in her forties, told Reuters at a polling station in Toulouse, southern France on Sunday.
"My choice is Francois Fillon because I don't want a right that is tainted by the left," said Harold Bakinsian, a 51 year-old architect voting in Frejus on the Mediterranean coast.
As the two candidates voted, Fillon told reporters: "It is the voters who are talking now, not the candidate."
Juppe meanwhile said he was proud of his campaign, but also complained over the way he had been cast on social media as soft on Islamist militancy – a sensitive subject in France, where more than 230 people have died in Islamist militant attacks since January last year.
"Some truths came out too late," he said.
Any registered voter can take part in the primary, making its outcome difficult to predict. The search for a consensus candidate to stop the National Front could help the more centrist Juppe, particularly if many voters from outside the ranks of the center-right take part.
"I voted for Alain Juppe because I fear Francois Fillon's economic program, too rightist and too conservative, will divide society too much," said Daniel Dunia, a Toulouse-based researcher in his forties who considers himself a leftwing voter.
Pollsters say the winner of the center-right primary will be the favorite to enter the Elysee palace, likely to place in the top two alongside Le Pen in a first round in April and defeat her in a run-off in May.
While polls show either Fillon or Juppe would beat Le Pen, Juppe would do so by a more comfortable margin. But the shock results in the British referendum and U.S. presidential contest mean forecasters' assumptions are being treated with caution.
Voter anger is sweeping aside establishment figures in Western countries, with Italy's Prime Minister Matteo Renzi forecast to lose a referendum on constitutional reform on Dec 4. Germany's Angela Merkel faces a fight for re-election next year.
French President Francois Hollande is so unpopular and his Socialists so divided that pollsters say he would be unlikely even to reach the run-off should he decide to run.
With France still under a state of emergency since Islamist militant attacks over the past two years, cultural tensions in a country that hosts Europe's biggest Muslim community have been central to the election debate.
Juppe praises France's diversity. Fillon says immigrants should assimilate to French cultural values.
"I think Juppe hasn't been firm enough on immigration questions and on the attacks," said Sonnard, the childminder in Toulouse.
There are also differences on foreign policy, with Fillon's pro-Russia stance raising eyebrows in Germany. On social policy, Fillon wants to curb adoption rights for same-sex couples.
Much of the arguments have centered on the economy.
Fillon proposes to cut twice as many public sector jobs as Juppe, lower corporate taxes, take on trade unions and reduce the role of the state, like his hero, Margaret Thatcher.
Fillon's photo-shopped face wearing the former British prime minister's distinctive hairstyle graced the front page of a left-leaning national newspaper last week. "You think I look like Margaret Thatcher?" he joked in English to reporters on Sunday.
Voters say they are fed up with France's near double-digit rate of unemployment — nearly double that of some European peers — and sluggish job creation in an economy that is forecast to grow an anemic 1.4 percent in 2016.
Hollande now has two weeks in which to decide whether to run for re-election. A win for Fillon and his hardline economic platform would give the 62-year-old Hollande a target to attack and could convince him to make a bid for a second five-year mandate against the odds. His Prime Minister, Manuel Valls, is also gearing up to stand.
The Socialist primaries are due to take place in January.